Belonuchus magnistylus, Márquez & Asiain, 2022

Márquez, Juan & Asiain, Julieta, 2022, Taxonomy of the Mexican species of Belonuchus Nordmann (Coleoptera: Staphylinidae), Zootaxa 5152 (1), pp. 1-129 : 35-36

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Belonuchus magnistylus

sp. nov.

Belonuchus magnistylus sp. nov.

Figs. 3a View FIGURE 3 , 14f View FIGURE 14 , 16h View FIGURE 16 , 18g View FIGURE 18 , 21h View FIGURE 21 , 26a View FIGURE 26

Total body length 11.2 mm. Black on head, antennae, pronotum, scutellum, visible abdominal segments 4–6 (except anterior borded of fourth) and abdominal styli. Reddish on elytra, legs, sterna (except the anterior half of prosternum), visible abdominal segments 1–3 and anterior border of fourth. Mandibles, maxillary and labial palpi, and genital segment brown.

Head: transverse; ratio length/width 0.73. Dorsal surface with punctures slightly sparser than in the majority of species; sulcate longitudinal midline visible in anterior half of head; front moderately foveate between antennal insertions. Eyes slightly longer than 0.5 times the cephalic lateral length, slightly protruding at sides. Antennomeres 4–6 elongate, 7 as long as wide, 8–10 slightly transverse. Mandibles 1.37 times longer than head; with two moderately separated teeth (basal and middle) of similar size; mandibular channel moderately developed; external margin slightly separated from internal margin at base, internal margin carinate, extending slightly forward of level of middle tooth. Apical palpomere of maxillary and labial palpi almost 1.25 times longer than preapical palpomere. Ventral surface with microscuplture as on dorsal surface, but less conspicuous and with very fine, sparse punctures. Head 1.19 times wider than pronotum. Neck in ventral view with coarser microsculpture than on ventral surface of head.

Thorax: each dorsal row of pronotum with five punctures; pronotum slightly longer than wide (ratio 1.13) and almost as wide at anterior corners as at posterior corners (ratio 1.03). Scutellum with punctation denser than on elytra, latter with fine and sparse punctation. Prosternum slightly elevated behind anterior margin. Intercoxal process of mesoventrite shield-shaped; discal transverse ridge moderately visible, with similar shape as intercoxal process and not meeting it laterally. Profemur with external row of spines initiating near basal third and not reaching apex, not even reaching level of first apical spine of internal margin, not more than 10 short spines; with three or four internal spines near apex longer than external spines. Metatrochanter modified like elongate hook, curved and acute at apex, almost as long as half length of metafemur; metafemur curved at level of overlap with hook and slightly in front; metatibia with internal part weakly curved in anterior third. Tarsomeres dorsally flattened, but not very distinctly.

Abdomen: first three visible abdominal tergites with posterior basal transverse carina well developed, adjacent area clearly depressed, less so on tergite 3; depression with dense wide-superficial punctures that decrease in density posteriad on each tergite; entire surface of each tergite additionally with moderately dense and fine punctures. All sternites with wide-superficial punctures denser than on tergites, but concentrated at anterior 1/4 to 1/2, on remaining surface of sternites these punctures are sparse and combined with fine punctures. Male pregenital sternite with U-shaped emargination at posterior margin ( Fig. 16h View FIGURE 16 ). Male genital sternite moderately elongate (2.6 times longer than wide), slightly asymmetrical, anterior portion occupying 40% and posterior portion 60% of its length, apical emargination deep ( Fig. 18g View FIGURE 18 ). Abdominal styli black and broad (as wide as, or slightly wider than apex of metafemur), with curved sides (more on external side) and apical zone flattened; ventrally with a series of 5–6 black and thickened setae placed before apex ( Fig. 14f View FIGURE 14 ).

Aedeagus: length 1.9 mm; oval-elongate shape; apex subacute, quite broad; in ventral view, basal half wider than apical half, mainly in comparison with apical portion where the sides are gradually becoming narrower toward apex; in lateral view, basal half is notably wider than apical half, oval-rounded shape; internal sac visible ( Fig. 21h View FIGURE 21 ).

Variability. Total body length in males 11.55 mm (range 11.5–11.6), in females 10.3 mm (without variation); ratio length/width of head in males 0.74 (range 0.72–0.76), in females 0.89 (without variation); ratio mandibular length/cephalic length in males 1.345 (range 1.33–1.36), in females 0.84 (without variation); ratio cephalic width/ pronotal width in males 1.185 (range 1.18–1.19), in females 1.06 (range 1.04–1.08); ratio length/width of pronotum in males 1.125 (range 1.12–1.13), in females 1.19 (without variation); ratio anterior width/posterior width of pronotum in males 1.04 (range 1.03–1.05), in females 1.00 (without variation). In addition, there is a variation in the color of the last or the last two antennomeres, which may be brown or even lighter; on the prosternum a transverse line can be present or not that delimits the elevated area; a female specimen has the procoxae and mesocoxae, and the prosternum and mesoventrite brown (dark); in one female the fourth visible abdominal segment is black in basal half and reddish in apical half; in two males, the emargination at the posterior margin of the pregenital sternite was more pronounced.

Taxonomic comments. Among the other three species with enlarged abdominal styli in males, B. magnistylus may be more easily confused with B. alternans , since they have the fourth visible abdominal segment mostly black; in the taxonomic comments of this last species their differences have been commented. The other two species with enlarged abdominal styli are B. confusus and B. trochanterinus , but they are distinguished from B. magnistylus because the fourth visible abdominal segment is all reddish.

Etymology. The name is a combination of “magnus” and “stylus” to highlight one of its diagnostic characteristics, the large styli.

Type material (six males, five females): Holotype (male, CC-UAEH) : “ México: Chiapas, San Cristóbal de las Casas, Reserva Biológica Huitepec , ladera NE, bosque de encino, 2238m, N16°14’798”, W92°40’848”, en pera podrida, 21-XI-1999, J. Márquez col. Paratypes: Same data as holotype (3, CC-UAEH; 2, MAAS). Mexico: Chiapas: “cerca de San Juan Panana, (cerca de El Triunfo), cultivo de café y selva media perturbada, 1480 m, N15°23’920”, W92°30’412”, en hojarasca y rocas de riachuelo, 22-XI-1999, J. Márquez col.” (1, MAAS) . “ San Cristobal de las Casas, Carretera SCLC-Sta. Rosa , 1km N El Puerto, bosque de encino, 1687m, N16°26’899”, W92°24’186”, NTP-80, 21-XI al 3-XII-1999, J. Márquez col.” (2, MAAS) . “ San Cristobal (near), Sendero Nat. Oxyoquet, 2-VII-1991 / human dung pitfall trap, T. K. Phillips & P. Kovarik, Field Museum of Natural History ” (m 1, FMNH) . “ San Cristobal (near), Sendero Nat. Oxyoquet, 2-VII-1991 / human dung pitfall trap, T. K. Phillips & P. Kovarik, Field Museum of Natural History ” (m 1, FMNH) .


Natuurhistorisch Museum Maastricht, Botany Department


Field Museum of Natural History